One-step arylthiolation to aromatic compounds by disulfide radical cations generated from oxidation of diaryl disulfides with aluminium chloride

Abstract

Reactions of di(phenyl and 4-tolyl) disulfides 1a and 1b with PhX 3a–e (X = H, Me, Et, Ph and Cl) in the presence of AlCl₃ at 25 °C give diaryl sulfides 4–6 by aromatic arylthiolation via the disulfide radical cations 2, along with thiophenols 7 formed in the incomplete reactions. Competitive intramolecular reactions of 2a also yield diphenyl sulfide 4a or/and thianthrene 8. However, the reactions of bis(4-chlorophenyl and 4-fluorophenyl) disulfides 1c and 1d selectively lead to the aromatic arylthiolation in high yields. The Hammett ρ = −8.8 at 25 °C for the phenylthiolation in the reactions of 1a is more negative than that (ρ = −7.0 at −30 °C) using SbCl₅ instead of AlCl₃, and the value ρ = −8.0 for the arylthiolation using 1d is less negative than that using 1a. These and the other mechanistic aspects support the arylthiolations via2.